Interfacial engineering to boost photoresponse performance and stability of V2O5/n-Si heterojunction photodetectors

Abstract

Transitional metal oxides (TMOs) have demonstrated as a promising alternative to doped layers in high-efficient crystalline silicon heterojunction solar cells. However, the unintentional oxidation causes serious carrier recombination at the interface, which accounts for the low photoelectric conversion efficiency and poor stability. Herein, a self-powered, broad-band, fast-response V2O5/n-Si heterojunction photodetectors (PDs) are fabricated by thermal evaporation of an ultrathin V2O5 thin films on nanoporous pyramid silicon structures. By interfacial engineering with structural optimization and surface methyl passivation, the photodetection performance and stability of V2O5/n-Si PDs can be significantly enhanced. The V2O5/n-Si heterojunction PDs demonstrate a high on/off ratio of 1.4×104, fast-response speed of 9.5 μs, high responsivity of 185 mA W−1 (@940 nm) and high specific detectivity (1.34×1012 Jones). Based on the energy band alignment analysis, the excellent photoresponse performance is mainly attributed to the efficient carrier separation after surface passivation by methyl group. Additionally, the built-in electric field at the interface also accelerates the charge carrier separation. Our work would contribute to the fabrications of other TMOs-based heterojunctions, and give some enlightening insights into the understanding of carrier transportation in heterojunctions.